David Cameron will go down in history as the man who lost Europe and split the UK

Former prime minister David Cameron has resigned as an MP. He leaves parliament with his political record in tatters. More than any other single person, Cameron is responsible for the UK's breakup with Europe and the potential collapse of the UK itself:

He called the EU referendum believing (wrongly) that the UK would vote to Remain.

The Leave majority required him to resign as Prime Minister in disgrace.

Britain leaving the EU may yet trigger the collapse of the United Kingdom as a whole.

SNP leader Nicola Sturgeon trying to get a new Scottish Independence referendum to stay in the EU.

The Brexit result emboldened nationalists across Europe, who are now demanding their own in/out referenda, threatening the entire existence of the EU.

S&P Global said today, "The uncertainty surrounding the U.K's future outside of the E.U. and the associated economic risks, which we think are pronounced and predominantly skewed to the downside, is likely to gradually take its toll."

This is all Cameron's fault.

His historic gamble was promising in 2013 to hold an in/out EU referendum in order to appease the nationalist wing of the Conservative Party and, hopefully, snuff out the UKIP threat that was peeling votes from the Tories. His bet was that Britain would do the expected thing: To realise that its economic bread was buttered on the European side.

In hindsight, Cameron's bet was a colossal blunder that could lead to the end of the "United Kingdom" of England, Wales, Scotland and Northern Ireland as a whole. And it looks as if that one wrong decision from Cameron could destroy the whole thing.

The Scotland move is obvious: The SNP has only become more popular since the Scottish referendum of 2015, and English Leave votes just demonstrated to even loyal British Scots that the folks down South can't be trusted, again. It is really hard to see the Scottish majority re-emerging to stay inside a UK that isn't European.

UKIP emerged triumphant with the brexit result. It may yet go on to build itself into a potent third force, like the National Front in France.

The Ireland thing, however, is just astonishing.

Why should Northern Ireland be pulled out of the EU by English and Welsh votes? It's a legitimate, real question that has never been asked before. It has just never come up! Yet Cameron made it a foreseeable reality.

"I thought about this long and hard over the summer," Cameron told Sky News. "In my view with modern politics, with the circumstances of my resignation, it isn't really possible to be a proper backbench MP as a former prime minister." He said it would only be a "diversion" if he stayed on and "I don't want to be that distraction."

This map from the BBC shows what "the circumstances of my resignation" really are: it reveals how geographically split Cameron has left the country. Scotland is European. England and Wales are "independent." And Northern Ireland, separated by a sea from both Scotland and the mainland, voted to remain European.

Irish reunification outside of the UK suddenly, weirdly, makes a lot of sense (although Irish Unionists will oppose it bitterly) both politically and geographically.

It will be incredibly sad if Great Britain disappears because of this. There was nothing inherently wrong with the UK. It wasn't engaged in civil war. No one was deprived of the vote. We didn't divide the home countries into castes or ranks. People's movement wasn't restricted. Their wealth was not taxed or confiscated unfairly. (True, Northern Ireland was occupied by British troops for many years - but everyone hated that and it was solved in 1994 through the democratic process.) This nation has existed peacefully and prosperously with itself since 1707.

Europe, too: The EU is a deeply flawed institution but it has one shining achievement: There has not been a World War in Europe for 66 years. People forget that the original premise of the EU was to bind the countries together so that it would be economically impossible for them to wage war on each other, as they did twice in the last century. It worked.

That's the true tragedy here. We had a United Kingdom and peace in Europe in 2013. And then Cameron opened his mouth.

When Cameron resigned as PM this summer, he said, "I will do everything I can as Prime Minister to steady the ship over the coming weeks and months but I do not think it would be right for me to try to be the captain that steers our country to its next destination." It is interesting that he admitted "the ship" was not steady. Because he will forever go down in history as the captain who drove it onto the rocks.

It is interesting that he admitted "the ship" was not steady. Because he will forever go down in history as the captain who drove it onto the rocks.